A lateral field effect transistor (LDMOS), as a commonly used high-voltage semiconductor device, is widely used in power management, LCD and LED driving, ESD protection and other fields. There are usually two application methods, simulation application and switch application. When the LDMOS is used as a switch, the device needs to have a very low on-resistance (the source-drain resistance of the device in the linear region), so as to reduce the switching power consumption. In LDMOS, the length of the channel is far less than that of the drift region, the resistance of the drift region predominates over the on-resistance of the device, and therefore all the switch LDMOSs need as far as possible to have increased doping concentration of the drift region, reduced length of the drift region, and increased thickness of the drift region, so as to attain the purpose of reducing the on-resistance. However, LDMOS must meet the requirement of the breakdown voltage, and both the increase of the doping concentration of the drift region and the reduction of the length are limited to an extent. The increase of the thickness of the drift region can non-epitaxial process, which may result in excessive lateral diffusion and a too large short-channel effect, however. An epitaxial LDMOS can form a thick drift region, but the process cost is higher.